木質材料 局所的水蒸気爆砕処理による効果発現の含水率依存性

Abstract

The pretreatment of moist wood by local steam explosion was attempted to improve the permeability of wood, and its effect on drying rate was investigated.In a convective kiln drying of the specimens having low initial moisture content, the drying rate was not improved by local steam explosion. On the contrary, for the specimens having high initial moisture content, the drying rate was increased by this pretreatment. The increase of drying rate by local steam explosion was observed in the whole range of moisture content under the radio-frequency/vacuum drying process even if the specimens have low moisture content. The impregnation of dye solution was also improved by the pretreatment regardless of initial moisture content.From these results, it is clear that the local steam explosion is effective in improving the permeability of wood and the occurrence of the treatment effect is dependent on drying process. The effectiveness of pretreatment in convective kiln drying was assumed to be affected by the initial condition of moisture because free water can not move to the surface by capillary tension force in the case that free water is not continuous in wood. The permeability is easily improved in the RF/vacuum drying process where the transport water through wood is done in the form of vapor by pressure differential.